7G8 



Popular Science Monthly 



Size of Picture on Screen with Lenses 



of Different Focuses When Using 



Standard Slide 



The front board, which carries the 

 objective, may be made first. The 

 design is shown in Fig. 4, and the 

 openings and general form should be 

 described by measuring from the center 

 line. The large openings may readily be 

 cut with a fine jeweler's saw, or if the 



e 



shown in Fig. 6. These cylinders are 

 made from thin sheet brass accurately 

 cut and shaped h\ means of a tinner's 

 roll. An accommodating tinner will 

 usually be glad to perform such a small 

 ser\'ice without charge. The smaller 

 cylinder should slide easily within the 

 large one. It is then sweat-soldered to 

 the lens-board, care being taken to see 

 that it is exactly centered. 



The slide-carrier holder, with the 

 dimensions of its parts, is shown in Figs. 

 7, 8 and 9. The piece shown in F"ig. 7 

 is soldered to the larger cylinder, D, 

 Fig. 2 and the smaller ring of brass wire, 

 Fig. 10, is sweated on at the junction. 



Side elevation 



O 



\ 



Lamp hood fn do/fed 



//nes \ 



front elevation 



P/an 



Fig. 2. The objective assembled. The lenses are usually supplied in a mounting, with 

 a flange and knurled adjusting knob, which actuates a rack and pinion arrangement 



builder has a power-drill, lhe\' may be 

 roughly drilled and finished uji to line 

 with a file. The lens-opening will ob- 

 viously have to conform to the diameter 

 of the lens-barrel or its flange, which is 

 made (A sheet brass, Y^ i'l- thick and 

 secured to the board with maciiine 

 screws. 



The lens-board is held upright b\ iwo 

 rods of brass. Fig. 5, which slide into 

 brass tubes. Upon these tubes the 

 remainder of the instrument is assembled. 

 The dimensions of the telescoping c>'lin- 

 ders which supjilant the bellows are 



When llu' c\liiider is to be soldered on, 

 the rods and lubes should be in place and 

 the one cylinder telescoped within the 

 other, to insure accurate centering. As 

 the assembled drawing shows. Fig. 2, 

 the U|)right /? is grijiped between the 

 collars Fwliich are forced over the tubes 

 and soldered in pi, ice. The dimensions 

 of the collars are all gi\en in Fig. II. 

 The |)aris of liu' slide-carrier holder are 

 asseml)led by means of screws; and 

 clamjiing-screws in the top piece are 

 arranged to engage the slide-carrier and 

 secure it in ihe proper posilioii. 



